Of course, a little probing reveals a different story. The article states that Dreamcast sales ". . . were up 156.6 percent between July 23 and Sept. 30 . . ." but the story of the Playstation 2 shortages didn't break until September 28. Unless Sega had a banner couple of days there at the end of September, other factors are at work here.
The article mentions this fact in passing later on, pointing out that Sega has cut the price of the Dreamcast to $150, and has also been offering rebates for signing up for the Seganet online gaming service. Obviously these factors probably sold a lot more Dreamcasts between July and September than Sony's announcement did.
Of course, everything will probably be turned upside down when the PS2 actually launches, but it will be interesting to see how things end up. Will Sony dominate the Christmas season, or will PS2's lack of availability cause shoppers to seek out Sonic?